Method and device for diagnosing an error in an exhaust gas recirculation system

ABSTRACT

In a method for determining a faulty exhaust gas recirculation line in an exhaust gas recirculation system of an internal combustion engine having multiple exhaust gas recirculation lines, a quantity of gas indicated by a specified exhaust gas recirculation rate is provided proportionately via the exhaust gas recirculation lines in accordance with an exhaust gas recirculation apportioning ratio, and the method further includes: testing in order to recognize an error in the exhaust gas recirculation system; when the error is recognized, performing a modification of the exhaust gas recirculation apportioning ratio and renewed testing of the exhaust gas recirculation system; and determination of the faulty exhaust gas recirculation line as a function of a result of the renewed testing.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to internal combustion engines havingexhaust gas recirculation, in particular to internal combustion engineshaving a plurality of exhaust gas recirculation lines, such as ahigh-pressure exhaust gas recirculation line and a low-pressure exhaustgas recirculation line, and the present invention also relates tomethods for recognizing a type of error in such an exhaust gasrecirculation system.

2. Description of the Related Art

In internal combustion engines having exhaust gas recirculation, currentlegislation requires the recognition of the type of error in the exhaustgas recirculation system. In particular, it is to be recognized when theactual exhaust gas recirculation rate is too high or too low relative tothe exhaust gas recirculation rate that is to be set, because thisaffects the emissions of the internal combustion engine. In today'sengine systems, which have a high-pressure exhaust gas recirculationsystem, the type of error can be detected through suitable observationof sensors that are present, such as the hot-film air mass sensor formeasuring the mass flow of the supplied fresh air, the intake pipesensor for measuring an intake pipe pressure, and the like, andobservation of the reaction of the exhaust gas recirculation regulatingsystem. Modern engine systems have exhaust gas recirculation systemshaving two exhaust gas recirculation lines. A high-pressure exhaust gasrecirculation line connects the exhaust gas evacuation segment to anintake pipe at a position upstream from a turbine of a charge devicesuch as an exhaust gas turbocharger, while a low-pressure exhaust gasrecirculation line connects the exhaust gas evacuation segment to theair supply system at a position downstream from the turbine, at a regionbefore a compressor of the charge device. A transfer of theabove-described method for recognizing the type of error in the exhaustgas recirculation system to such an exhaust gas recirculation systemhaving two exhaust gas recirculation lines is not readily possible,especially without providing additional sensors. In particular, it isnecessary, in addition to determining an error and the type of error inthe exhaust gas recirculation system, also to find out in which of theexhaust gas recirculation lines the error has occurred.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect of the present invention, a method isprovided for determining a faulty exhaust gas recirculation line in anexhaust gas recirculation system having a plurality of exhaust gasrecirculation lines in an internal combustion engine, an exhaust gasquantity indicated by a specified exhaust gas recirculation rate beingprovided proportionately via the exhaust gas recirculation lines, inaccordance with an exhaust gas recirculation apportioning ratio. Themethod includes the following steps:

-   -   testing in order to recognize an error in the exhaust gas        recirculation system;    -   when the error is recognized, modification of the exhaust gas        recirculation apportioning ratio and renewed testing of the        exhaust gas recirculation system;    -   determination of the faulty exhaust gas recirculation line as a        function of a result of the renewed testing.

As a rule, errors are distinguished by recognizing different features ora resulting error pattern. Likewise, multi-stage diagnoses are known inwhich a first test yields a general suspicion of error, and in a secondstage for example an intrusive test is carried out, or the system isreferred to a workshop for further diagnosis.

As a reaction to a recognized error, up to now either the entire exhaustgas recirculation regulation is switched off, or, in the case of minorerrors, the regulation is continued with acceptance of larger tolerancesin the regulation.

For the case in which, in an exhaust gas recirculation system having aplurality of exhaust gas recirculation lines, the type of error can berecognized, in particular a throughput error, but it cannot berecognized in which of the exhaust gas recirculation lines the error hasoccurred, the above method provides modification of the apportioning ofthe exhaust gas recirculation to the exhaust gas recirculation lineswhen an error is recognized in the exhaust gas recirculation system. Thelocation of the error can be inferred as a function of a result of asubsequent renewed testing of the exhaust gas recirculation system.

In an exhaust gas recirculation system having two exhaust gasrecirculation lines, the apportioning of the exhaust gas recirculationtakes place as specified by an exhaust gas recirculation apportioningratio (AGR apportioning ratio, AGR fraction), such that given an AGRapportioning ratio of 0%, only a high-pressure exhaust gas recirculationline is used, and given an AGR apportioning ratio of 100% only alow-pressure exhaust gas recirculation line is used for the exhaust gasrecirculation. This method is carried out after an error has beenrecognized in the exhaust gas recirculation system, indicating a highflow error, i.e. an excessive gas mass flow is flowing via the exhaustgas recirculation system, or a low flow error, i.e. a too-low gas massflow is flowing via the exhaust gas recirculation system. Such an itemof error information can be obtained from various items of sensorinformation, which however do not enable pinpointing, i.e. assignment ofthe error to one of the exhaust gas recirculation lines.

The above method has the advantage that in a simple manner an assignmentof a recognized error to one of the exhaust gas recirculation lines inan exhaust gas recirculation system is possible. Because the operatingpoint of the internal combustion engine is not impaired by the use ofthe method, i.e. no excitation oriented to the regulation target isrealized in the system, it can be carried out almost entirely unnoticedby a driver of a motor vehicle operated with the internal combustionengine.

In addition, when the error is recognized the exhaust gas recirculationapportioning ratio can be modified in such a way that the quantity ofexhaust gas to be recirculated is recirculated completely through onlyone of the exhaust gas lines, an assignment of the error to one of theexhaust gas recirculation lines (pinpointing) being possible on thebasis of the type of error and the active exhaust gas recirculationline.

Alternatively, when the error is recognized the quantity of recirculatedexhaust gas through one of the exhaust gas recirculation lines can bemaintained, while the recirculation of exhaust gas through the otherexhaust gas recirculation line or lines can be stopped.

It can be provided that in order to maintain the exhaust gasrecirculation rate the target air quantity is adapted so as tocorrespond to the quantity of the exhaust gas recirculated through theone of the exhaust gas recirculation lines.

In particular, the selection of the exhaust gas recirculation linethrough which exhaust gas is exclusively recirculated after recognitionof the error can be made as a function of the exhaust gas recirculationapportioning ratio existing before the recognition of the error.

According to a specific embodiment, the selection of the exhaust gasrecirculation line can be carried out as a function of the result of athreshold value comparison with one or more threshold values.

It can be provided that the threshold value is fixed, or is selected asa function of an operating point of the internal combustion engine.

Alternatively, two threshold values can be provided in order to define arange of the exhaust gas recirculation apportioning ratio, in which theexhaust gas quantity to be recirculated is provided through a pluralityof exhaust gas lines even after the recognition of the error.

According to a specific embodiment, the testing can be carried out inorder to recognize a flow error, in particular a high flow error or alow flow error, of the exhaust gas recirculation system.

According to a further aspect of the present invention, a device isprovided for determining a faulty exhaust gas recirculation line in anexhaust gas recirculation system having a plurality of exhaust gasrecirculation lines in an internal combustion engine, an exhaust gasquantity indicated by a specified exhaust gas recirculation rate beingprovided proportionately via the exhaust gas recirculation lines inaccordance with an exhaust gas recirculation apportioning ratio. Thedevice is fashioned:

-   -   to carry out a test in order to recognize an error in the        exhaust gas recirculation system;    -   when the error is recognized, to modify the exhaust gas        recirculation apportioning ratio and to carry out a renewed test        of the exhaust gas recirculation system; and    -   to determine the faulty exhaust gas recirculation line as a        function of a result of the renewed testing.

According to a further aspect of the present invention, an engine systemis provided. The engine system includes:

-   -   an internal combustion engine;    -   an exhaust gas recirculation system having a plurality of        exhaust gas recirculation lines between an air supply system and        an exhaust gas evacuation segment;    -    and    -   the above-described device.

According to a further aspect of the present invention, a computerprogram product is provided that contains a program code that carriesout the above-described method when it is executed on a data processingdevice.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic representation of an engine system having anexhaust gas recirculation system having two exhaust gas recirculationlines.

FIG. 2 shows a block diagram illustrating the carrying out of the methodfor error assignment.

FIG. 3 shows a flow diagram illustrating the method for assigning arecognized error in the exhaust gas recirculation system.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows an engine system 1 having an internal combustion engine 2.Internal combustion engine 2 can be fashioned as a diesel engine, agasoline engine, or the like.

Air is supplied to internal combustion engine 2 via an air supply system3. The air is mixed with fuel and is combusted in cylinders 4 ofinternal combustion engine 2. Combustion exhaust gas is carried awayfrom cylinders 4 via an exhaust gas evacuation segment 6. The fuel canbe supplied to internal combustion engine 2 directly by injection intocylinders 4 or via an intake pipe segment 5 of air supply system 3.

A charge device 7 is provided that can be realized for example as anexhaust gas turbocharger. Charge device 7 has a turbine 71 in exhaustgas evacuation segment 6, which can be driven through exhaust gasenthalpy of the combustion exhaust gas. Turbine 71 is coupled to acompressor 72 that is situated in air supply segment 3 and that suctionsair from the surrounding environment and provides it, compressed to acharge pressure, in a charge pressure region 8 of air supply system 3.Charge pressure region 8 is a region situated immediately at the outputside of compressor 72.

In addition, a throttle valve 9 is provided in air supply system 3.Intake pipe segment 5 is situated downstream from throttle valve 9, i.e.between throttle valve 9 and internal combustion engine 2. An exhaustgas recirculation system is provided that includes a first exhaust gasrecirculation line 10, a so-called high-pressure exhaust gasrecirculation line, and a second exhaust gas recirculation line 11, aso-called low-pressure exhaust gas recirculation line.

First exhaust gas recirculation line 10 connects a region of exhaust gasevacuation segment 6 between internal combustion engine 2 and turbine 71of charge device 7 to intake pipe segment 5 of air supply system 3. Infirst exhaust gas recirculation line 10 there is provided a firstexhaust gas feedback valve 12 that enables setting of the exhaust gasmass flow flowing through first exhaust gas recirculation line 10.

Second exhaust gas recirculation line 11 connects a downstream region ofturbine 71 of charge device 7 to the inlet side of compressor 72. Insecond exhaust gas recirculation line 11 there is provided a secondexhaust gas recirculation valve 13 in order to enable setting of aquantity of the exhaust gas recirculated via second exhaust gasrecirculation line 11.

Exhaust gas recirculation lines 10, 11 can contain exhaust gasrecirculation coolers (not shown) in order to lower the temperature ofthe recirculated exhaust gas so that the density and thus the overallmass of the recirculated exhaust gas can be increased.

Internal combustion engine 2 is operated by a control unit 15. For thispurpose, via suitable sensors such as a hot-film air mass sensor 14,various pressure sensors, and the like, control unit 15 acquiresoperating states of engine system 1, and controls them by controllingactuators, such as throttle valve 9, of first and second exhaust gasrecirculation valve 12, 13, injection valves (not shown) for setting thequantity of fuel to be injected, and the like, in order to operateinternal combustion engine 2 in accordance with a specified torque FWMdesired by the driver as an external specification.

In such an exhaust gas recirculation system, having two (or more thantwo) exhaust gas recirculation lines 10, 11, errors can occur, so thatthe exhaust gas recirculation system has to be monitored, because errorsin the exhaust gas recirculation system, in particular errors in thesetting of a specified exhaust gas recirculation rate, can makeemissions worse. In particular, in the exhaust gas recirculation systemerrors can occur through which the set exhaust gas recirculation ratebecomes too low relative to the desired exhaust gas recirculation rate,e.g. when there is blockage or sooting in exhaust gas recirculationlines 10, 11, or becomes too high, e.g. when there is a leak in theexhaust gas recirculation system, or when there is a faulty exhaust gasrecirculation valve 12, 13.

Such a method first monitors the recirculated gas quantity throughplausibilization of sensor or model values. In particular, an error canbe recognized in the exhaust gas recirculation system by comparing anindication of the gas quantity flowing through the exhaust gasrecirculation lines, determined using a mass flow balance of thequantity of supplied fresh air and of the volume suctioned into internalcombustion engine 2 (as a function of rotational speed, number ofcylinders, and displacement volume), to an indication of a quantity ofgas flowing through the exhaust gas recirculation lines, this quantitybeing determined via the pressure ratio between a downstream and anupstream end of exhaust gas recirculation lines 10, 11 and a position ofthe relevant exhaust gas recirculation valve 12, 13. If the indications,obtained in different ways, of the quantity of gas flowing through theexhaust gas recirculation lines differ from one another, then it ispossible to infer an error. As a function of the mathematical sign ofthe difference, a high flow error, i.e. a situation in which thequantity of gas supplied to the air supply system by the exhaust gasrecirculation system is too high, or a low flow error, i.e. a situationin which the quantity of gas supplied to the air supply system by theexhaust gas recirculation system is too low, can be inferred.

In the following, the method for assigning a recognized error in theexhaust gas recirculation system to a relevant exhaust gas recirculationline 10, 11 is described on the basis of the block diagram shown in FIG.2 and the flow diagram shown in FIG. 3.

The block diagram shown in FIG. 2 illustrates the functions formonitoring engine system 1 when an error is present in the exhaust gasrecirculation system. The diagram of FIG. 2 schematically shows exhaustgas recirculation system 21, having exhaust gas recirculation valves 12,13, which can be set according to target specifications by exhaust gasrecirculation regulator 22.

Exhaust gas recirculation system 21 is monitored by a monitoring block23, for example in the manner described above, in order to determine thepresence of an error in exhaust gas recirculation system 21. A targetvalue block 27 specifies target values for the current operating staterelating to exhaust gas recirculation system 21. These target values arethe air mass flow {dot over (m)} of the fresh air supplied to internalcombustion engine 2, an exhaust gas recirculation rate r_(AGR), and anexhaust gas recirculation apportioning ratio r_(LPFRC) (AGR apportioningratio). Exhaust gas recirculation rate r_(AGR) indicates in what portioncombustion exhaust gas is to be fed into the air mass flow supplied tointernal combustion engine 2. AGR apportioning ratio r_(LPFRC) indicatesthe contributions that each of the exhaust gas recirculation lines 10,11 are supposed to provide. For example, an AGR apportioning ratior_(LPFRC) of 50% indicates that the quantity of recirculated exhaust gasthrough the two exhaust gas recirculation lines 10, 11 should beprovided in equal portions.

An AGR apportioning ratio r_(LPFRC) of 100%, in contrast, indicates thatthe quantity of recirculated exhaust gas is to be provided completelyvia second exhaust gas recirculation line 11, while an AGR apportioningratio r_(LPFRC) of 0% indicates that the quantity of recirculatedexhaust gas is to be supplied to the fresh air mass flow completelythrough first exhaust gas recirculation line 10.

A threshold value block 24 is provided to which AGR apportioning ratior_(LPFRC), generated by target value block 27 according to an exhaustgas recirculation strategy, is supplied, and that is activated as soonas monitoring block 23 has recognized an error. Threshold value block 24provides a diagnostic apportioning ratio r_(LPNeu) according to whichexhaust gas recirculation valves 12, 13 are to be set in order to permita more precise diagnosis of the recognized error. From the diagnosticapportioning ratio r_(LPNeu), the air mass flow {dot over (m)} that isto be provided, and the exhaust gas recirculation rate r_(AGR), in alimiting block 25 a limiting air mass flow {dot over (m)}_(neu) and alimiting exhaust gas recirculation rate r_(AGR) _(—) _(neu) aredetermined and are supplied to exhaust gas recirculation regulator 22.In addition, diagnostic apportioning ratio r_(LP) _(—) _(neu) issupplied to the limiting block in order there to apply possiblecomponent protective functions to diagnostic apportioning ratio r_(LP)_(—) _(neu).

Limiting block 25 modifies the supplied mass flow, exhaust gasrecirculation rate r_(AGR), and, as needed, diagnostic apportioningratio r_(LP) _(—) _(Neu) in order to carry out a component protectivefunction or similar functions. Limited air mass flow {dot over(m)}_(neu), limited exhaust gas recirculation rate r_(AGR) _(—) _(neu),and limited diagnostic apportioning ratio r_(LPlim) are supplied toexhaust gas recirculation regulator 22, which correspondingly setsexhaust gas recirculation valves 12, 13. Threshold value block 24 setseither 0% or 100% as monitoring apportioning ratio r_(LP) _(—) _(neu),as a function of whether AGR apportioning ratio r_(LPFRC) is above orbelow a threshold value S provided by a selection threshold value block26.

As indicated in the flow diagram of FIG. 3, the monitoring for an errortakes place in a querying step S1. If an error is recognized in exhaustgas recirculation system 21 (alternative: yes), then threshold valueblock 24 is activated and a jump takes place to step S2; otherwise(alternative: no) the query of step S1 is repeated.

In the query in step S2, it is now checked whether AGR apportioningratio r_(LPFRC) is above a specified threshold value S. If this is thecase (alternative: yes), then 100% is assumed as monitoring apportioningratio r_(LP) _(—) _(neu) (step S3); i.e., exhaust gas recirculation rater_(AGR) is provided completely through second exhaust gas recirculationline 11. Otherwise (alternative: no), 0% is provided as monitoringapportioning ratio r_(LP) _(—) _(neu); i.e., exhaust gas recirculationrate r_(AGR) is provided only via first exhaust gas recirculation line10 (step S4).

Threshold value S can be fixedly specified, or can also be defined as afunction of parameters that describe the operating point of internalcombustion engine 2, such as a rotational speed indication or a loadindication. In particular, threshold value S is applied in such a waythat when a changeover takes place to an exhaust gas recirculationthrough only one of exhaust gas recirculation lines 10, 11, the variantis selected that has the lowest additional pollutant emissions.

If, in step S3, monitoring apportioning ratio r_(LP) _(—) _(NEU) was setto 100%, then in a following step S5 the error monitoring carried out instep S1 is carried out again, and the location of the error in exhaustgas recirculation system 21 is inferred as a function of a reneweddetermination of the error recognized in step S1.

If in step S5 a so-called high flow error is recognized, i.e. the gasquantity conducted through exhaust gas recirculation system 21 exceedsthe desired gas quantity, then in step S6 an error in first exhaust gasrecirculation line 10 can be inferred. Otherwise, a jump takes place tostep S7, in which it is checked whether the recognized type of errorcorresponds to a low flow error. A low flow error corresponds to anerror in which the exhaust gas quantity supplied to air supply system 3is lower than the desired exhaust gas quantity. In this case, an errorin second exhaust gas recirculation line 11 can be inferred (step S8).If the method detects only the error types high flow error and low flowerror, then the query in step S7 can be omitted, and, using a method ofexclusion, in the absence of a high flow error it can be inferred that alow flow error must be present.

If, in step S4, monitoring apportioning ratio r_(LPneu) was set to 0%,then in a following step S9 the error monitoring carried out in step S1is carried out again, and the location of the error in exhaust gasrecirculation system 21 is inferred as a function of a reneweddetermination of the error recognized in step S1.

If, in step S9, a so-called high flow error is recognized (alternative:yes), i.e. the quantity of gas conducted through exhaust gasrecirculation system 21 exceeds the desired quantity of gas, then instep S10 an error in second exhaust gas recirculation line 11 can beinferred. Otherwise (alternative: no), in step S9 a jump takes place tostep S11, in which it is checked whether instead a low flow error ispresent. If a low flow error is present (alternative: yes), then in stepS12 an error in first exhaust gas recirculation line 10 is inferred.

Otherwise (alternative: no), i.e. in the case in which neither a highflow error nor a low flow error is present, in step S13 it is determinedthat an assignment of an error to one of exhaust gas recirculation lines10, 11 cannot be carried out.

If the method detects only the error types high flow error and low flowerror, then the query in step S11 can be omitted, and, using anexclusion method, in the absence of a high flow error it can be inferredthat a low flow error must be present.

In an alternative specific embodiment, in threshold value block 24 itcan be provided that, instead of adapting the monitoring apportioningratio r_(LP) _(—) _(neu) to 0 or 100%, it is provided that when AGRapportioning ratio r_(LPFRC) is above specified threshold value S, theexhaust gas recirculation is carried out only using second exhaust gasrecirculation line 11, according to the corresponding specified AGRapportioning ratio r_(LPFRC), while first exhaust gas recirculation line10 is completely closed. If AGR apportioning ratio r_(LPFRC) is smallerthan threshold value S, then first exhaust gas recirculation line 10 iscontrolled in accordance with AGR apportioning ratio r_(LPFRC) andsecond exhaust gas recirculation line 11 is completely closed. In thisway, exhaust gas recirculation rate r_(AGR) is reduced. In order to beable to further carry out the method in as emissions-neutral a fashionas possible, air mass target value r_(DESVAL) should also becorrespondingly adapted as follows:

r _(DESVAL) _(—) _(neu) =r _(DESVAL) ×r _(LPFRC), if r _(LPFRC) >S and

r _(DESVAL) _(—) _(neu) =r _(DESVAL)×(1−r _(LPFRC)), if r _(LPFRC) <S.

In this way, the set exhaust gas recirculation rate remains constant.

Through selection threshold value block 26, instead of a specifiedthreshold value S it is also possible for two selection threshold valuesSa, Sb to be provided. The definition of monitoring apportioning ratior_(LP) _(—) _(neu) is then as follows:

r _(LP) _(—) _(neu)=0 if r _(LPFRC) <Sa

r _(LP) _(—) _(neu) =r _(LPFRC) −Sa)/(Sb−Sa) if Sa≦r _(LPFRC) ≦Sb

r _(LP) _(—) _(neu)=100 if r _(LPFRC) >Sb.

If threshold values Sa and Sb are close to each other, there results anexhaust gas recirculation operation using only one of exhaust gasrecirculation lines 10, 11 with adequate frequency.

The above-described method can usefully also be expanded to include theadditional recognition of errors in air supply system 3, such as errorsin hot-film air mass sensor 14 and errors in the charge pressure.

What is claimed is:
 1. A method for determining a faulty exhaust gasrecirculation line in an exhaust gas recirculation system of an internalcombustion engine having a plurality of exhaust gas recirculation lines,wherein a quantity of gas indicated by a specified exhaust gasrecirculation rate is provided proportionately via the exhaust gasrecirculation line in accordance with an exhaust gas recirculationapportioning ratio, the method comprising: testing the exhaust gasrecirculation system in order to recognize an error in the exhaust gasrecirculation system; when the error is recognized, performing (i) amodification of the exhaust gas recirculation apportioning ratio and(ii) a renewed testing of the exhaust gas recirculation system; anddetermining a faulty exhaust gas recirculation line as a function of aresult of the renewed testing of the exhaust gas recirculation system.2. The method as recited in claim 1, wherein, when the error isrecognized, the exhaust gas recirculation apportioning ratio is modifiedin such a way that the quantity of exhaust gas to be recirculated isrecirculated completely through only one of the exhaust gasrecirculation lines.
 3. The method as recited in claim 1, wherein, whenthe error is recognized, the quantity of recirculated exhaust gasthrough one of the exhaust gas recirculation lines is maintained whilethe recirculation of exhaust gas through the remaining exhaust gasrecirculation lines is stopped.
 4. The method as recited in claim 3,wherein a target air quantity is adapted in accordance with themaintained quantity of the exhaust gas recirculated through the one ofthe exhaust gas recirculation lines in order to maintain the exhaust gasrecirculation rate.
 5. The method as recited in claim 2, wherein theexhaust gas recirculation line through which exhaust gas is exclusivelyrecirculated after the error is recognized is selected as a function ofthe exhaust gas recirculation apportioning ratio existing before therecognition of the error.
 6. The method as recited in claim 5, whereinthe selection of the exhaust gas recirculation line through whichexhaust gas is exclusively recirculated is carried out as a function ofa result of at least one threshold value comparison with at least onethreshold value.
 7. The method as recited in claim 6, wherein the atleast one threshold value is one of fixed or selected as a function ofan operating point of the internal combustion engine.
 8. The method asrecited in claim 6, wherein two threshold values are provided in orderto define a range of the exhaust gas recirculation apportioning ratio inwhich the quantity of exhaust gas to be recirculated is provided througha plurality of exhaust gas recirculation lines after the recognition ofthe error.
 9. The method as recited in claim 2, wherein the testing ofthe exhaust gas recirculation system is carried out in order torecognize a flow error of the exhaust gas recirculation system.
 10. Adevice for determining a faulty exhaust gas recirculation line in anexhaust gas recirculation system of an internal combustion engine havinga plurality of exhaust gas recirculation lines, wherein a quantity ofgas indicated by a specified exhaust gas recirculation rate is providedproportionately via the exhaust gas recirculation line in accordancewith an exhaust gas recirculation apportioning ratio, the devicecomprising: means for testing the exhaust gas recirculation system inorder to recognize an error in the exhaust gas recirculation system;means for performing, when the error is recognized, the following: (i) amodification of the exhaust gas recirculation apportioning ratio and(ii) a renewed testing of the exhaust gas recirculation system; andmeans for determining a faulty exhaust gas recirculation line as afunction of a result of the renewed testing of the exhaust gasrecirculation system.
 11. A non-transitory computer-readable datastorage medium storing a computer program having program codes which,when executed on a computer, performs a method for determining a faultyexhaust gas recirculation line in an exhaust gas recirculation system ofan internal combustion engine having a plurality of exhaust gasrecirculation lines, wherein a quantity of gas indicated by a specifiedexhaust gas recirculation rate is provided proportionately via theexhaust gas recirculation line in accordance with an exhaust gasrecirculation apportioning ratio, the method comprising: testing theexhaust gas recirculation system in order to recognize an error in theexhaust gas recirculation system; when the error is recognized,performing (i) a modification of the exhaust gas recirculationapportioning ratio and (ii) a renewed testing of the exhaust gasrecirculation system; and determining a faulty exhaust gas recirculationline as a function of a result of the renewed testing of the exhaust gasrecirculation system.